The purpose of this study was to determine the usefulness of calculating jump take-off momentum in rugby league (RL), by exploring its relationship with sprint momentum, due to the latter being an important attribute to this sport. Twenty-five male RL players performed three maximal-effort countermovement jumps (CMJs) on a force platform and three maximal effort 20 m sprints (with split times recorded). Jump take-off momentum and sprint momentum (between 0-5 m, 5-10 m and 10-20 m) were calculated (mass multiplied by velocity) and their relationship determined. There was a very large positive relationship between both jump take-off and 0-5 m sprint momentum (r = 0.781, p < .001) and jump take-off and 5-10 m sprint momentum (r = 0.878, p < .001). There was a nearly perfect positive relationship between jump take-off and 10-20 m sprint momentum (r = 0.920, p < .001). Jump take-off and sprint momentum demonstrated good-excellent reliability and very large-near perfect associations (61-85% common variance) in a RL cohort, enabling prediction equations to be created. Thus, it may be practically useful to calculate jump take-off momentum as part of routine CMJ testing of RL players, and other collision-sport athletes, to enable indirect monitoring of sprint momentum.